Typically, an accumulator of lithium-ion type successively comprises a negative electrode, an electrolyte, and a positive electrode.
Its operation in discharge cycle is ensured by the transfer of lithium ions from the negative electrode (anode) to the positive electrode (cathode) and by the transfer of electrons from the negative electrode (anode) to the positive electrode (cathode) due to an external circuit. The transfers are reversible to enable the accumulator to charge.
The electrodes are generally associated with current collectors which ensure electron displacements therebetween.
The electrolyte generally comprises a lithium salt, for example, lithium bis(trifluoromethane)sulfonimide (LiTFSI) or lithium hexafluorophosphate (LiPF6).
During the operation of the accumulator, the electrolyte salt may possibly partially decompose, and thus alter the properties of the accumulator. As an example, the LiPF6 salt may generate HF-type compounds. The presence of LiTFSI salt in an electrolyte containing a solvent of ester carbonate type may cause the anodic dissolution of the aluminum which is used as a current collector for positive electrodes. This especially occurs when the electrode material comprises a lamellar oxide taken to a potential greater than 3.7 V vs. Li0.
Prior art comprises various solutions enabling to overcome this issue, among which the use of a co-salt in the electrolyte, the increase of the salt concentration, the use of a current collector made of a material different from aluminum, but also the development of new salts or of new solvents.
However, such solutions generally turn out being expensive and unreliable as to their results.
A pretreatment of aluminum with the LiBOB (lithium bis(oxalate)borate) lithium salt has also been provided (Journal of Electrochemical Society, 2006 153 (9) B365-B369).
In any event, there still is a need to develop variations which are relatively easy to use, adapted to any type of salt and of electrolyte solvent.